Rotation Period of C/2006 P1 (McNaught) Through Morphological Analysis with Narrowband Imaging

TL;DR

This paper determines the rotation period of comet C/2006 P1 (McNaught) by analyzing morphological features in narrowband images, revealing a rotation period of approximately 11.8 hours through advanced image processing techniques.

Contribution

It introduces a morphological analysis method using narrowband imaging and image enhancement to accurately measure the comet's rotation period, demonstrating the technique's effectiveness.

Findings

Rotation period of 11.8 hours identified.

Dynamic coma structures observed and analyzed.

Consistent morphological features validated the rotation measurement.

Abstract

This study presents findings from narrowband imaging of comet C/2006 P1 (McNaught) using the 3.6-metre New Technology Telescope (NTT) at La Silla, Chile. Observations commenced on January 27, 2007, 15 days after perihelion, and continued until February 4, with additional sessions from February 25 to 28. Imaging was conducted using the ESO Multi-Mode Instrument (EMMI) in both broadband (B, V, R) and six comet-specific narrowband filters (CN, C3, C2, NH2, blue and red continuum). Various image processing techniques were employed to enhance structural features, including azimuthal mean/median division and subtraction, azimuthal renormalisation, and division by inverse profile, as well as the Larson-Sekanina technique. These enhancements revealed dynamic coma structures, with jets transitioning from spiral patterns to linear or fan-like shapes over time. The consistency of morphological patterns across different processing methods validated their authenticity. The periodic recurrence and temporal evolution of CN coma features in narrowband images indicate a nucleus rotation period of 11.8 h, consistent with stable active regions and rotationally modulated outgassing near perihelion.